The menu is not showing anymore after updating to WordPress 4.4.
Only on the homepage it shows correctly, but it should be the same on all pages. The same menu is set as main and mobile navigation on all pages. Website: http://www.3dv.nl

Update: I’ve found a way around it, but only if the menu is the default menu.
The menu I’m using is called ‘3DV’, and is set as default menu. When I set the menu of a page to ‘3DV’ (from the dropdown list) the menu doesn’t show. But when I choose ‘default’ it does show correctly… Hope this helps narrowing down the cause of the problem.